In the wake of complaints from both Google and Mozilla about web browsers running on Windows RT (also known as Windows 8 ARM), the European Commission said today in a statement it will make sure Microsoft stays true to a previous agreement that was supposed to allow competition for all web browsers on Windows PCs.

The Commission is aware of these allegations and will remain vigilant that Microsoft fully complies with its commitments under the Commission's 2009 decision on browsers. This decision applies to Microsoft's Windows operating system for PCs.

The statement refers to the agreement where Microsoft is now required to display a screen in Windows that offered linked to not just Internet Explorer but other web browsers.

The agreement, however, is just for Windows on PCs, according to Colombani. In theory, Microsoft could claim that devices that run on Windows RT are not real PCs. Both Mozilla and Google had complained that Microsoft has limited access to Windows RT for their Chrome and Mozilla web browsers. Microsoft's web browser competition agreement with the EU is supposed to last for five years, meaning it will expire in 2014.